It is generally known that a wheel bearing apparatus can support a wheel of vehicle with respect to a suspension apparatus and detect a rotation speed of a wheel of vehicle to control the anti-lock braking system (ABS). Such a bearing apparatus generally includes a sealing apparatus arranged between inner and outer members. The inner and outer member rotates relative to each other via rolling elements. The rotational speed detecting apparatus includes a magnetic encoder with magnetic poles alternately arranged along its circumference. The magnetic encoder is integrally formed with the sealing apparatus. A rotational speed sensor detects change of the magnetic poles of the magnetic encoder caused by the rotation of a wheel.
In general, the rotational speed sensor is mounted on a knuckle after the wheel bearing apparatus has been mounted on the knuckle to form part of a suspension apparatus. Recently, a wheel bearing apparatus has been proposed to receive a rotational speed sensor in order to reduce the size of the wheel bearing apparatus. Also, it eliminates the complexity of adjusting an air gap between the rotational speed sensor and a magnetic encoder.
FIG. 24 illustrates one example of a wheel bearing apparatus. This wheel bearing apparatus includes an outer member 101, forming a stator member, secured on a knuckle (not shown). The outer member 101 includes double row outer raceway surfaces 101a (only one of them is shown). A wheel hub 103 is inserted into the outer member 101, via double row balls 102. An inner ring 104 is fit onto the wheel hub 103.
One inner raceway surface (not shown) is formed on the outer circumference of the wheel hub 103. The other inner raceway surface 104a is formed on the outer circumference of the inner ring 104. The inner ring 104 is press-fit onto a cylindrical portion 103a that axially extends from the inner raceway surface of the wheel hub 103. The double row balls 102 are contained and rollably held by cages 105 between the outer and inner raceway surfaces.
The wheel hub 103 has, on its one end, a wheel mounting flange to mount a wheel. The inner ring 104 is axially immovably secured by a caulked portion 106 to the wheel hub 103. The caulked portion 106 is formed by plastically deforming, radially outward, the end of the cylindrical portion 103a. The inboard-side end of the outer member 101 is provided with a first cap (i.e. cover) 107 to prevent leakage of lubricating grease contained in the wheel bearing. Also, the cap 107 prevents entry of rain water or dust into the wheel bearing from the outside.
The first cap 107 is formed of austenitic stainless steel sheet, such as SUS 304, non-magnetic metal sheet, such as aluminum alloy, or non-metallic sheet, such as a plastic sheet. It has a bottom portion 108, a flat portion 108a at the bottom portion 108 and a cylindrical portion 109. The cylindrical portion 109 axially extends from the outer periphery of the bottom portion 108. In addition, a flange-like abutting portion 110 extends radially outward from the cylindrical portion 109. Thus, the abutting portion 110 abuts against the inboard-side end face of the outer member 101.
The bottom portion 108 has the flat portion 108a and a bulged portion 108b arranged at the center of the bottom portion 108. The bulged portion 108b bulges toward an axially inboard-side from the flat portion 108a. In addition, a sealing member 111, of elastomer such as rubber, is arranged on the outer circumference of the cylindrical portion 109.
The first cap 107 is secured on the outer member 101. The cylindrical portion 109 is press-fit, via interference fit, into the axially inboard-side end of the outer member 101. In addition, the outboard-side surface of the abutting portion 110 of the first cap 107 abuts against the inboard-side end face of the outer member 101. The outboard-side surface of the flat portion 108a closely opposes a magnetic encoder 112 press-fit onto the inner ring 104.
A second cap (i.e. sensor holding plate) 114 holds a sensor 113. The second cap 114 is press-fit, via interference fit, onto the axially inboard-side end of the outer member 101. The second cap 114 is formed of ferrous metal, such as carbon steel or stainless steel, non-ferrous metal such as aluminum alloy or plastics. The second cap 114 is shaped to have a generally dish-like shape. It includes a flat disk-shaped bottom portion 115 and a cylindrical fitting portion 116 bent axially outboard from the bottom portion 115. A through aperture 117 is formed at a radially outward position of the bottom portion 115. A mounting aperture 118 is formed at a position near the center of the bottom portion 115. A nut 119 is secured around the mounting aperture 118 by welding, adhesion, press-fitting or caulking.
The fitting portion 116 of the second cap 114 is press-fit onto the axially inboard-side end of the outer member 101. Thus, the abutting portion 110 of the first cap 107 is sandwiched axially on both sides between the bottom portion 115 and the outer member 101. Thus, the second cap 114 can prevent the first cap 107 from being displaced toward the axially inboard-side direction and cover the first cap 107 from the axially inboard-side via a space 120.
In order to secure the sensor 113 to the bearing apparatus, the tip end of the sensor 113 is first inserted through the aperture 117 into the space 120. The tip end of the sensor 113 abuts against the axially inboard-side surface of the flat portion 108a of the bottom portion 108. A bolt 121 is fastened to the nut 119 by passing the nut 119 through an aperture formed in a mounting flange 122 of the sensor 113.
As can be understood from the description above, the first cap 107 encloses an inside space 123 where the magnetic encoder 112 is arranged. The second cap 114 can prevent the first cap 107 from being pushed and displaced toward the magnetic encoder 112 by the abutting operation of the detecting portion (tip end) of the sensor 113. Also, the second cap 114 can exactly limit the axial displacement of the first cap 107. In addition, the second cap 114 can prevent the generation of deformation of the first cap 107 by any force that would cause deterioration in detection accuracy.
A radially inward force is applied to the bottom portion 108 of the first cap 107 when the cylindrical portion 109 of the first cap 107 is press-fit into the end of the outer member 101. The applied energy is used to deform the bulged portion 108b. As the result of which, it is possible to effectively suppress the deformation of the flat portion 108a and exactly limit the axial position of the flat portion 108a. (See, JP 2010-180912 A.
In such a prior art wheel bearing apparatus, the first cap 107 is press-fit into the inner circumference of the end of the outer member 101. The second cap 114 is press-fit onto the outer circumference of the end of the outer member 101. Accordingly, the cylindrical fitting portion 116 of the second cap 114 would expand into a horn-like shape and slip off from the outer member 101 when the outer member 101 is deformed due to vibrations or application of a large load. In addition, the rigidity of the prior art second cap 114 of the outer circumference-fitting type is smaller than that of the sensor holding plate of the inner circumference-fitting type. Thus, it is believed that insufficient strength and rigidity of the sensor holding plate of the outer circumference-fitting type cannot maintain stable detection accuracy for a sensor 113.
It is, therefore, an object of the present disclosure to provide a wheel bearing apparatus that can solve problems of prior art and thus achieve improved detection accuracy and sealability by increasing the rigidity of the second cap.
To achieve the above mentioned object, a wheel bearing apparatus comprises an outer member with double row outer raceway surfaces integrally formed on its inner circumference. An inner member includes a wheel hub and at least one inner ring. The wheel hub is integrally formed, on its one end, with a wheel mounting flange. A cylindrical portion axially extends from the wheel mounting flange, The inner ring is press-fit onto the cylindrical portion of the wheel hub. The inner member outer circumference includes double row inner raceway surfaces. The double row inner raceway surfaces oppose the double row outer raceway surfaces. Double row rolling elements are contained between the inner raceway surfaces and outer raceway surfaces of the inner member and outer member. A pulser ring is adapted to fit onto the outer circumference of the inner ring. The pulser ring has magnetic characteristics alternately and equidistantly varying along its circumferential direction. A cup-shaped second cap, press-formed from steel sheet, is fit onto the inboard-side end of the outer member. A rotational speed sensor is mounted on the second cap at a radially outer position. The rotational speed sensor is arranged opposite to the pulser ring, via a predetermined axial air gap. A cup-shaped first cap is press-fit into the inner circumference of an inboard-side end of the outer member, via a predetermined interference. The first cap is press-formed from non-magnetic austenitic stainless steel sheet. The first cap has a cylindrical fitting portion press-fit into the inner circumference of the inboard-side end of the outer member. A disk portion extends radially inward from the fitting portion and opposes the pulser ring, via a small axial gap. The rotational speed sensor is arranged opposite to the pulser ring, via the first cap. The speed sensor abuts against or is close to the disk portion of the first cap. The second cap is press-fit into the inner circumference of an inboard-side end of the outer member via a predetermined interference.
The wheel bearing apparatus has a pulser ring adapted to fit onto the outer circumference of the inner ring, with magnetic characteristics alternately and equidistantly varying along its circumferential direction. A cup-shaped second cap, press-formed of steel sheet, is fit on the inboard-side end of the outer member. A rotational speed sensor is mounted on the second cap at a radially outer position. The rotational speed sensor is arranged opposite to the pulser ring via a predetermined axial air gap. A cup-shaped first cap is press-fit into the inner circumference of an inboard-side end of the outer member, via a predetermined interference. The first cap is press-formed from non-magnetic austenitic stainless steel sheet. The first cap has a cylindrical fitting portion press-fit into the inner circumference of the inboard-side end of the outer member. A disk portion extends radially inward from the fitting portion and opposes the pulser ring via a small axial gap. The rotational speed sensor is arranged opposite to the pulser ring, via the first cap. The speed sensor abuts against or is close to the disk portion of the first cap. The second cap is press-fit into the inner circumference of an inboard-side end of the outer member, via a predetermined interference. Thus, it is possible to provide a wheel bearing apparatus with reliability and that can achieve improved detection accuracy and sealability by increasing the rigidity of the second cap.
A first fitting surface is formed on the inner circumference of the inboard-side end of the outer member. A second fitting surface is formed on the inner circumference of the outer member at a further inboard-side from the first fitting surface, via a stepped portion. The first cap is press-fit onto the first fitting surface. The second cap is press-fit onto the second fitting surface. This makes it possible to suppress the press-fitting stroke minimum and improve the assembling workability as well as to prevent deformation of the first cap during the press-fitting process. Thus, this improves the reliability of the wheel bearing apparatus.
The first fitting surface and the second fitting surface are simultaneously ground by a formed grinding wheel with the double row outer raceway surfaces. This makes it possible to improve the accuracy in the roundness and coaxiality of each fitting surface. Thus, this improves the sealability of the fitting portions. In addition, the simultaneous grinding can reduce working steps and thus manufacturing costs.
The second cap has a cylindrical fitting portion fit on the inner circumference of the inboard-side end of the outer member. A flange portion is formed as a double bent portion. The flange portion extends radially outward from the fitting portion. The flange portion is adapted to closely contact against the inboard-side end face of the outer member. A bottom portion extends radially inward from the flange portion to close an inboard-side opening of the outer member. An insert aperture is formed in the bottom portion at a position corresponding to the pulser ring. The rotational speed sensor is inserted and mounted in the aperture. This makes it possible to increase the rigidity of the second cap. Thus, this improves the positioning accuracy in the rotational speed sensor. In addition, it is possible to suppress air gap variation between the rotational speed sensor and the pulser ring. Thus, this obtains stable detection accuracy even if the outer member and the inner member would be relatively inclined by a lateral load applied to them from a wheel.
A depth of the second fitting surface is larger than the thickness of the second cap. This makes it possible to make the fitting portion of the second cap to project from the inner circumference of the end of the outer member. Thus, this prevents foreign matter from entering within the second cap and from accumulated in this place.
The inner circumference between the first fitting surface and the second fitting surface of the outer member is formed as a tapered surface. Its radius gradually increases at an angle toward the opening of the outer member. This makes it possible to smoothly displace foreign matter that enters within the second cap without residence.
The second cap is coated with a rust-preventing coating film by cation electro-deposition. This makes it possible to keep a smooth surface on the fitting surface while embedding micro irregularities and preventing easy peeling of the rust-preventing coating film during the press-fitting of the outer member. Accordingly, it is possible to prevent the generation of rust in the fitting portion of the second cap for a long term. Thus, this obtains good sealability in the fitting portion between the second cap and the outer member.
The second cap is formed from rust-prevented steel sheet. An elastic member is integrally adhered on the second cap at a portion contacting the outer member. This makes it possible to improve the sealability and reliability of the second cap.
The elastic member of the second cap is formed from rust-preventing coating film by cation electro-deposition. This makes it possible to prevent the generation of rust on the abutting portion for a long term and to keep good sealability.
The elastic member of the second cap is a packing member formed from synthetic rubber integrally adhered to the second cap by vulcanized adhesion.
A bulged portion is formed on the bottom portion of the second cap at a region nearer to the ground. A drain is radially cut-through and formed in a bottom wall of the bulged portion. This makes it possible to effectively discharge foreign matter outside without being disturbed by a knuckle of a vehicle even when the knuckle projects to the inboard-side from the end of the outer member.
The drain is formed as a tongue by punching and bending the bottom wall of the bulged portion. According to this structure, the tongue can close an opening of the drain and perform a protecting wall to prevent entry of muddy water or pebbles. Thus, this can maintain the speed detecting accuracy and improve the reliability of an ABS.
A radially reduced portion is formed between the fitting portion and the disk portion of the first cap. An elastic member, of synthetic rubber, is integrally adhered to the radially reduced portion by vulcanized adhesion. The elastic member is arranged so that it does not project from the side surface of the disk portion toward the inboard-side. This prevents the elastic member from interfering with the rotational speed sensor. The elastic member is formed with an annular projection projecting radially outward from the fitting portion. According to this structure, the annular projection of the elastic member is elastically deformed and pressed onto the inner circumference of the outer member during press-fitting of the first cap. Thus, the sealability of the fitting portion can be improved.
The second cap is formed from steel sheet. The second cap is press-fit, via a predetermined interference, into the inner circumference of the inboard-side end of the outer member in an overlapped state with the first cap. This makes it possible to provide a wheel bearing apparatus that improves the detecting accuracy and sealability. Also, it can reduce the manufacturing cost while reducing assembling steps by press-fitting both the first and second caps by a single press-fitting operation.
A stepped portion is formed on an open end of the fitting portion of the second cap. The stepped portion and the fitting portion of the first cap have predetermined width dimensions. An open end of the fitting portion of the first cap is press-fit into the second cap until the open end of the fitting portion of the first cap abuts against a wall of the stepped portion. This makes it possible to accurately set the air gap between the rotational speed sensor, mounted in the aperture of the second cap, and the pulser ring. Also, it prevents deformation of the first cap if the thickness of the sheet forming the first cap is small.
The fitting portion of the first cap and the fitting portion of the second cap have predetermined width dimensions. The fitting portion of the first cap is press-fit into the fitting portion of second cap until the end face of the fitting portion of the first cap abuts against the bottom portion of the second cap. This also makes it possible to accurately set the air gap between the rotational speed sensor, mounted in the aperture of the second cap, and the pulser ring. Also, it prevents deformation of the first cap if the thickness of the sheet forming the first cap is small.
The fitting portion of the first cap and the fitting portion of the second cap have predetermined width dimensions. The fitting portion of the second cap is press-fit into the fitting portion of first cap until the end face of the fitting portion of the second cap abuts against the disk portion of the first cap. This also makes it possible to accurately set the air gap between the rotational speed sensor, mounted in the aperture of the second cap, and the pulser ring. Also, it prevents deformation of the first cap if the thickness of the sheet forming the first cap is small.
The second cap has a flange portion formed as a double bent portion. The double bent portion extends radially outward from the fitting portion. The double bent portion closely contacts against the inboard-side end face of the outer member. The fitting portion of the first cap and the fitting portion of the second cap have predetermined width dimensions. The fitting portion of the first cap is press-fit onto the fitting portion of second cap until the open end of the fitting portion of the first cap abuts against the side surface of the flange portion. The second cap is press-fit into the outer member until the side surface of the flange portion abuts against the end face of the outer member. This also makes it possible to accurately set the air gap between the rotational speed sensor mounted in the aperture of the second cap, and the pulser ring. Also, it prevents deformation of the first cap if the thickness of the sheet forming the first cap is small.
The elastic members of synthetic rubber are integrally adhered by vulcanized adhesion to the connected portion between the fitting portion of the first cap and the fitting portion of the second cap. The elastic member is elastically deformed and press-contacted with the fitting surface of the outer member. The elastic member is elastically deformed and closely contacted to the fitting portion of the first cap. This makes it possible to improve the sealability of the first cap.
The wheel bearing apparatus has an outer member integrally formed on its inner circumference with double row outer raceway surfaces. An inner member includes a wheel hub and at least one inner ring. The wheel hub is integrally formed, on its one end, with a wheel mounting flange. A cylindrical portion axially extends from the wheel mounting flange. The inner ring is press-fit onto the cylindrical portion of the wheel hub. The inner member is formed on its outer circumference with double row inner raceway surfaces that oppose the double row outer raceway surfaces. Double row rolling elements are contained between the inner raceway surfaces and outer raceway surfaces of the inner member and outer member. A pulser ring is adapted to be fit onto the outer circumference of the inner ring. The pulser ring has magnetic characteristics alternately and equidistantly varying along its circumferential direction. A cup-shaped second cap, press-formed from steel sheet, is fit on the inboard-side end of the outer member. A rotational speed sensor is mounted at a radially outer position on the second cap. The rotational speed sensor is arranged opposite to the pulser ring, via a predetermined axial air gap. A cup-shaped first cap is press-fit into the inner circumference of an inboard-side end of the outer member, via a predetermined interference. The first cap is press-formed from non-magnetic austenitic stainless steel sheet. A first cap cylindrical fitting portion is press-fit into the inner circumference of the inboard-side end of the outer member. A disk portion extends radially inward from the fitting portion and opposes the pulser ring, via a small axial gap. The rotational speed sensor is arranged opposite to the pulser ring, via the first cap. The speed sensor abuts against or is close to the disk portion of the first cap. The second cap is press-fit into the inner circumference of an inboard-side end of the outer member, via a predetermined interference. Thus, it is possible to provide a wheel bearing apparatus with reliability that can achieve improved detection accuracy and sealability by increasing the rigidity of the second cap.